[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 092355
SWOMCD
SPC MCD 092354
KYZ000-TNZ000-INZ000-ILZ000-MOZ000-MSZ000-ARZ000-100130-

MESOSCALE DISCUSSION 2142
NWS STORM PREDICTION CENTER NORMAN OK
0554 PM CST SUN DEC 09 2012

AREAS AFFECTED...CNTRL THROUGH NERN AR...WRN TN...EXTREME SERN
MO...SRN IL AND WRN KY

CONCERNING...TORNADO WATCH 677...

VALID 092354Z - 100130Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 677 CONTINUES.

SUMMARY...STORMS WILL CONTINUE TO POSE A SEVERE THREAT INTO MID
EVENING OVER REMAINING PART OF TORNADO WATCH 677 FROM SRN IL...WRN
KY...EXTREME SERN MO...CNTRL THROUGH ERN AR AND EXTREME WRN TN.
GREATEST TORNADO POTENTIAL THROUGH 02Z IS EXPECTED FROM ECNTRL
THROUGH NERN AR...AND POSSIBLY EXTREME NWRN TN. BAND OF STORMS THAT
HAVE DEVELOPED AHEAD OF THE MAIN LINE ACROSS WRN TN MAY POSE AT
LEAST A MODEST SEVERE THREAT. OVERALL THREAT DOES NOT APPEAR
SUFFICIENT TO WARRANT ANOTHER WW AT THIS TIME...BUT AREA WILL
CONTINUE TO BE MONITORED.

DISCUSSION...STORMS CONTINUE DEVELOPING PRIMARILY ALONG A SEWD
ADVANCING COLD FRONT FROM SRN IL...SERN MO THROUGH NERN...CNTRL AND
SWRN AR. BEST PARAMETER SPACE FOR A COUPLE TORNADOES REMAINS FROM
CNTRL THROUGH ECNTRL/NERN AR WHERE A MORE FAVORABLE COMBINATION OF
INSTABILITY AND LOW LEVEL SHEAR IS INDICATED WITH 150-250 M2/S2 0-1
KM STORM RELATIVE HELICITY AND WHERE STORMS REMAIN AT LEAST
SEMI-DISCRETE. WITHIN THIS ZONE...THE PRIMARY LIMITING FACTOR
APPEARS TO BE ONSET OF NOCTURNAL COOLING AND A STABILIZING BOUNDARY
LAYER WHICH MAY BE OFFSET SLIGHTLY BY MODEST THETA-E ADVECTION ALONG
A 40 KT SSWLY LLJ.

FARTHER NORTH FROM SERN MO INTO SRN IL...STORMS HAVE EVOLVED INTO A
PREDOMINANT LINEAR MODE WITH AN ATTENDANT GREATER THREAT FOR
ISOLATED DAMAGING WIND. HOWEVER...A TORNADO OR TWO ALSO REMAIN
POSSIBLE WITH ANY EMBEDDED SUPERCELL STRUCTURES. SEVERE THREAT MAY
SPREAD A LITTLE NORTH AND EAST OF CURRENT WW INTO WRN KY IN
ASSOCIATION WITH THIS ACTIVITY NEXT COUPLE HOURS...BUT EXTENT AND
DEGREE OF THREAT IN THIS REGION WILL BE LIMITED BY INCREASINGLY
MARGINAL INSTABILITY.

BAND OF CONVECTION THAT HAS DEVELOPED IN WARM SECTOR ACROSS WRN TN
IS EMBEDDED WITHIN FAVORABLE LOW LEVEL AND DEEP SHEAR FOR
SUPERCELLS. HOWEVER...ACTIVITY IS FORMING ALONG ERN EDGE OF
INSTABILITY/MOIST AXIS AND CHARACTER OF CONVECTION SO FAR SUGGESTS
UPDRAFTS ARE NOT PARTICULARLY ROBUST DUE TO LIMITED BUOYANCY.

..DIAL.. 12/09/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...OHX...PAH...MEG...LZK...

LAT...LON   37458744 35948827 34808964 34079130 34229325 35629202
            36499067 37958821 37458744


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